MRC/CSO Social and Public Health Sciences Unit

Published 30th September 2021

The Medical Research Council (MRC) / National Institute for Health Research (NIHR) complex intervention research framework has been published today.

The framework is aimed at a broad audience including health researchers, funders, clinicians, health professionals, policy and decision makers.

It is intended to help:

• Researchers choose appropriate methods to improve research quality
• Research funders to understand the constraints on evaluation design
• Users of evaluation to weigh up the available evidence in the light of methodological and practical constraints.

Defining complex interventions

The new framework provides an updated definition of complex interventions, highlighting the dynamic relationship between the intervention and its context. Complex interventions are widely used in the health service, in public health practice, and in areas of social policy that have important health consequences, such as education, transport, and housing.

Tackling the important questions

The new framework supports the development or identification, feasibility testing, evaluation and implementation of complex interventions. The framework outlines that complex intervention research can take an efficacy, effectiveness, theory-based or systems perspective depending on what is known already and what further evidence would be most useful.

It highlights a trade-off between precise unbiased answers to narrow questions and more uncertain answers to broader, more complex questions. This framework aims to increase the utility of data so that it will provide more valuable information to decision makers and improve health in practice.

Using the framework’s core elements

There are four main phases of research: intervention development or identification, e.g. from policy or practice, feasibility, evaluation, and implementation.

At each phase, the guidance suggests that six core elements should be considered: 

1. how does the intervention interact with its context?
2. what is the underpinning programme theory?
3. how can diverse stakeholder perspectives be included in the research?
4. what are the key uncertainties?
5. how can the intervention be refined?
6. do the effects of the intervention justify its cost? 

These core elements can be used to decide whether the research should proceed to the next phase, return to a previous phase, repeat a phase, or stop.

Developing the framework

The development of the framework was led by the MRC/CSO Social and Public Health Sciences Unit alongside co-authors and a Scientific Advisory Group chaired by Professor Martin White (MRC Epidemiology Unit, University of Cambridge) and including representation from all the NIHR Boards and MRC’s Population Health Science Group. The work was informed by a scoping review, a workshop with international experts, an open consultation (with broad response from researchers of all career stages, funders, the public, and journal editors), and further targeted consultation with experts in relevant fields.

The update was jointly commissioned by the Medical Research Council (MRC) and the National Institute of Health Research (NIHR).

Extremely influential

Professor Nick Wareham, Chair of MRC’s Population Health Sciences Group, said:

“Previous versions of the guidance on the development and evaluation of complex interventions have been extremely influential and are widely used in the field. We are delighted that the successful partnership between MRC and NIHR has enabled the guidance to be updated and extended. It is particularly important to see how the new framework brings in thinking about the interplay between an intervention and the context in which it is applied.”

Stimulating debate

Dr Kathryn Skivington, Research Fellow, MRC/CSO Social and Public Health Sciences Unit and lead author of the framework, said:

“The new and exciting developments for complex intervention research are of practical relevance and I feel sure they will stimulate constructive debate, leading to further progress in this area.”

Patients benefit

Professor Hywel Williams, NIHR Scientific and Coordinating Centre Programmes Contracts Advisor, said:

 “This updated framework is a landmark piece of guidance for researchers working on such interventions. The updated guidance will help researchers to develop testable and reproducible interventions that will ultimately benefit NHS patients. The guidance also represents a terrific collaborative effort between the NIHR and MRC that I would like to see more of.”

Previous guidance

In 2006, the MRC published guidance for developing and evaluating complex interventions, building on the framework that had been published in 2000. These documents have been highly influential, and the accompanying papers published in the BMJ are widely cited.

Interest in complex interventions has increased rapidly in recent years. Given the pace and extent of methodological development, there was a need to update the core guidance and address some of the remaining weaknesses and gaps.

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First published: 30 September 2021